In U.S. patent application Ser. No. 5,699 filed Jan. 23, 1979 in the name of Robert W. Luebke, and now U.S. Pat. No. 4,296,884, and entitled Containment Reservoir and Method, there is disclosed a reservoir arrangement formed with a flexible liner laid in an earthern containment space for catching petroleum based liquids discharged from railroad vehicles, such as diesel locomotives, on a railroad track section. The present invention provides an improvement over the arrangement and method disclosed in Ser. No. 5,699, now U.S. Pat. No. 4,296,884.